UPDATE 4-Four U.S. Air Force helicopter crew believed killed in British crash

LONDON, Jan 7 (Reuters) - Four crew members on board a U.S.
military helicopter were believed to have been killed when their
aircraft crashed in eastern England during a routine training
operation on Tuesday, police and a Pentagon official said.

The helicopter, assigned to the 48th Fighter Wing based at
the nearby U.S. air base RAF Lakenheath, went down at about 1800
GMT on marshland on the north Norfolk coast, a rural area about
130 miles (209 km) northeast of London.

"We can confirm that one of our HH-60G Pave Hawk helicopters
went down outside Cley during a low-level flying exercise," said
a spokesman at the USAF base.

The four crew members "are presumed dead," a Pentagon
official said.

"Sadly we believe that at this time all four of the crew are
deceased," added Superintendent Roger Wilson of Norfolk Police
in comments to reporters.

Police said next of kin would be informed before further
details on the victims were released.

There was no immediate information as to the cause of the
crash. The Pave Hawk is made by Sikorsky Aircraft Co, a unit of
United Technologies Corp.

Police said a 400 metre (quarter-mile) area had been
cordoned off at the crash site, a nature reserve, while it was
determined from the U.S. military what munitions the helicopter
was carrying at the time.

No one in the surrounding area had been in any danger,
Wilson said.

The U.S. Air Force website said the primary mission of the
Pave Hawk helicopter, a highly modified version of the Army
Black Hawk, was "to conduct day or night operations into hostile
environments to recover downed aircrew or other isolated
personnel during war."

It added each aircraft had an automatic flight control
system, night vision goggles and a forward looking infrared
system "that greatly enhances night low-level operations", along
with anti-ice features to cope with adverse weather.

Lakenheath is also home to Europe's only F-15 fighter wing,
and local media reported that F-15 planes had been flying over
the crash site.

In 2001, two single-seat F-15Cs from Lakenheath crashed
while on a low-flying training mission over Scotland, killing
both pilots.